## Adds 1 or more characters to the end of message (based on a mathematical algorithm)

## Two types: Checksum and CRC

## Checksum

- Calculated by adding decimal values of each character in the message,
- Dividing the total by 255. and
- Saving the remainder (1 byte value) and using it as the checksum
- 95% effective

## Cyclic Redundancy Check (CRC)

- Computed by calculating the remainder to a division problem:

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